Control valves for the regulation of fluid flow are found in a great variety of applications in a wide array of industries. For example, in automotive vehicles, fluid control valves are used in the regulation of both lubricant and coolant flow.
The conventional fluid control valve includes a valve body having a valve assembly cylinder, an inlet port and an outlet port. The conventional fluid control valve further includes a rotatably movable valve positioned within the valve assembly cylinder of the valve body. The rotatably movable valve includes a valve stem and a gate or cone or other means for interfering with the flow of a fluid through the body by movement into or out of a valve seat formed in the valve body. To close the valve, the gate or cone is brought into contact with the seat formed in the valve body. A return spring is conventionally provided to selectively return the valve to either the closed or open condition.
It is known in the art to use shape memory alloy in the production of valves. Shape memory alloy is lightweight material that experiences deformation in response to thermal dynamics. This alloy provides a good alternative to hydraulic, pneumatic or motorized actuators. When heated either by ambient temperature or by an electric current, shape memory alloy assumes its original, non-deformed shape. When cooled, shape memory alloy assumes a deformed shape.
While shape memory alloys may be formed from a variety of alloyed material, the most common types are alloys of copper-aluminum-nickel and nickel-titanium. Shape memory alloy can exist in two phases, the first being an austenite phase and the second being a martensite phase. The latter phase is achieved when the alloy is subjected to cooling.
Valves that utilize shape memory alloy today can be divided into two categories. The first category includes shape memory alloy valves having linear displacement mechanisms. The second category includes shape memory alloy valves having complex rotatable systems.
Examples of both types of valves are known in the art. Of the former type, reference may be made to U.S. Pat. No. 6,427,712, issued on Aug. 6, 2002, to Ashurst for AMBIENT TEMPERATURE SHAPE MEMORY ALLOY ACTUATOR. This reference teaches an actuator that includes a valve having a stem 13 and a plug 10 positioned at the end of the stem 13. An SMA spring 14 works in conjunction with a bias spring 15 to move the stem 13 and its associated plug 10 between opened and closed positions relative to a drain hole 20. According to this reference, “[m]ovement of stem 13 (the actuating element) between the two positions may be substantially linear.”
An additional example of a valve that incorporates a shape memory alloy to function linearly may be found in UK Patent Application 2 107 829 A, filed on Mar. 18, 1982, by Dudley Vernon Steynor for THERMOSTATIC VALVES AND SOLAR WATER HEATING SYSTEMS INCORPORATING SAME. According to this reference, a “displaceable valve member [2] may comprise a poppet-type valve member which is normally biased by a spring [5] towards its seat [3], i.e., towards a valve-closed position. The shape memory effect (SME) actuator may comprise a coil spring [8] formed from an SME brass, for example, a Delta metal alloy, which expands and contracts axially with respective increases and decreases in temperature.”
A further example of a valve that incorporates a shape memory alloy to function linearly may be found in Korean Patent Application 20100035500 A, filed Apr. 5, 2010, by Pak Sil Sang for AUTOMATIC THERMOSTATIC CONTROL VALVE. According to this reference, the automatic temperature control valve includes “a bias spring [3] and a shape memory alloy spring [12] in an overlapped state.” The bias spring 3 and the shape memory alloy spring 12 overlap. The valve allows for the automatic bypass of a supply of water when the valve senses that the temperature of the water changes. The shape memory alloy spring 12 reacts to the change in water temperature and selectively allows or restricts the passage of water thereby.
Of the latter type of valve that includes shape memory alloy valves having complex rotatable systems. reference may be made to U.S. Pat. No. 8,172,811, issued on May 8, 2012, to Roe for DRUG DELIVERY PUMP DRIVE USING A SHAPED MEMORY ALLOY WIRE. This patent is directed “to a drug delivery pump drive using a shape memory alloy to advance a plunger piston to deliver a liquid drug from a container.” Particularly, “a SMA wire [12] is provided in a linear solenoid arrangement [110] with a spring return [122] to provide reciprocating linear motion. A set of concentric (inner and outer) tubes [124, 126] having matching facing helical slots [130] with bearings [132] therebetween is provided to convert the reciprocating linear motion into reciprocating rotary motion.” The patented pump drive of this patent is thus highly complex and costly to manufacture.
An additional example of a known shape memory alloy valves having a complex rotatable system is found in U.S. Pat. No. 6,684,904, issued on Feb. 3, 2004, to Ito for VARIABLE PRESSURE VALVE APPARATUS. This patent is directed to a valve that is provided with a shape memory spring. According to this patent, “[w]hen the shape memory alloy spring varies in length, a feed ratchet performs linear movement to rotate a cam wheel.” Specifically, “a temperature change cause deformation in the shape memory alloy spring 10 and expands or extends the shape memory alloy spring 10 to press an end face of a large diameter part of the feed ratchet 12 toward the return spring 11.” The feed ratchet 12 is thus rotated and causes a cam wheel 13 to move a surge spring 15 that acts upon a ball valve 17. The patented variable pressure valve of this patent is also highly complex and costly to manufacture.
As the above-discussed references illustrate, known fluid control valves that incorporate shape memory alloy biasing elements are either ineffective at translating linear motion into rotary motion or are of complex designs and have numerous parts, both aspects contributing to an expensive valve that may be difficult to produce and maintain. In addition, known valves do not provide for gradual changes in the position of the valve in response to certain conditions, such as temperature.
Accordingly, as in so many areas of valve technology, there is room in the art of fluid flow controlling valves for a practical and effective valve that is relatively inexpensive to produce and to maintain, that efficiently converts linear motion to rotary motion, and which provides infinite and selectable changes in position.